The present invention provides an oral DNA composition for improving an impaired immunity associated with chronic infection of hepatitis B virus HBV and for suppressing transgene expression for a protrated period of time comprising an attenuated strain of bacterial cells which preferentially target phagocytic cells of the intestinal mucosa, and which serve as a vehicle for a plasmid vector carrying one or more genes or complementary DNA coding for at least a portion of a hepatitis B viral protein or peptide. Given orally, the DNA composition causes a transient and self-limiting infection of the intestinal tract through autolysis of the bacterial cells and release of the plasmid after gaining entry into infected host cells.; A promotor contained within the plasmid allows for expression of the HBV genes in the eurokaryotic environment, the viral products of which help to booster a cell-mediated immunity to clear the infection and reverse a state of immune tolerance characteristic of HBV chronic infection.

The present invention provides an oral DNA composition for improving an impaired immunity associated with chronic infection of hepatitis B virus HBV and for suppressing transgene expression for a protrated period of time comprising an attenuated strain of bacterial cells which preferentially target phagocytic cells of the intestinal mucosa, and which serve as a vehicle for a plasmid vector carrying one or more genes or complementary DNA coding for at least a portion of a hepatitis B viral protein or peptide. Given orally, the DNA composition causes a transient and self-limiting infection of the intestinal tract through autolysis of the bacterial cells and release of the plasmid after gaining entry into infected host cells.; A promotor contained within the plasmid allows for expression of the HBV genes in the eurokaryotic environment, the viral products of which help to booster a cell-mediated immunity to clear the infection and reverse a state of immune tolerance characteristic of HBV chronic infection.